如何设置UITextField的“padding”值

最近在学习仿公司App时，遇到这样一个需求，搜索框的最左侧有个小icon，icon后面紧跟着placeholder。看图：

从代码中看，iOS同学（已离职）是这么搞的：

1. 先创建一个通栏的UIView用addSubview添加到self.view上

2. 然后创建一个UITextField，addSubview到上一步中创建的UIView上

3. 再创建一个UIImage类型的icon，addSubview到上一步中创建的UITextField上

4. 使用setText方法将提示文本直接赋值到UITextField，为了让提示文字“搜索商品”与icon之前保持一定的距离，居然写了这么一行代码，看注释

看代码：

- (void)initTopMenuBar{
    self.navigationController.navigationBar.hidden = YES;
    
    UIView *bgView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 320, 64)];
    [bgView setBackgroundColor:[UIColor whiteColor]];
    [self.view addSubview:bgView];
    
    UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(15, 20, 48, 44)];
    imageView.contentMode = UIViewContentModeCenter;
    [imageView setImage:[UIImage imageNamed:@"event_logo2"]];
    [self.view addSubview:imageView];

    UITextField *searchBar = [[UITextField alloc]initWithFrame:CGRectMake(73, 29, 232, 25)];
    searchBar.layer.cornerRadius = 12.5;
    searchBar.layer.masksToBounds = YES;
    searchBar.font = [UIFont systemFontOfSize:12];
    searchBar.delegate = self;
    searchBar.backgroundColor  = [BBColorUtils colorWithFloat:236 alpha:1.0];
    [searchBar setTextColor:[UIColor whiteColor]];
 
    // 吐槽！ 虽然我还在学习iOS开发阶段，虽然解决问题的方式有很多种，虽然条条大道通罗马，但是对于这种low代码也实在是看不下去。。。
    [searchBar setText:@"        搜索商品"];
    [bgView addSubview:searchBar];
    
    
    UIImageView *eventMagnifier = [[UIImageView alloc] initWithFrame:CGRectMake(7, 2, 20, 20)];
    eventMagnifier.image = [UIImage imageNamed:@"icon_title_search"];
    [searchBar addSubview:eventMagnifier];
    eventMagnifier.userInteractionEnabled = NO;
    
}

其实UITextField有placeholder属性的，这里用setText来做提示文案，还得在事件处理逻辑中去处理隐藏的问题，相当繁琐。。。

好了，吐槽完了，接着将我搜索到的相对正常一点的方法整理出来。

关键点：leftView，leftViewMode，rightView，rightViewMode

放上我改进之后的代码：

- (void)initSearch
{
    // 隐藏导航标题
    self.navigationController.navigationBar.hidden = YES;
    
    UIView *backgroudLayer = [[UIView alloc] initWithFrame:CGRectMake(0, 0, ScreenWidth, 64)];
    [backgroudLayer setBackgroundColor:[UIColor whiteColor]];
    [self.view addSubview:backgroudLayer];
    
    
    UIImageView *logo = [[UIImageView alloc] initWithFrame:CGRectMake(15, 20, 48, 44)];
    logo.contentMode = UIViewContentModeCenter;
    [logo setImage:[UIImage imageNamed:@"logo"]];
    [self.view addSubview:logo];
    
    
    UITextField *searchText = [[UITextField alloc] initWithFrame:CGRectMake(73, 29, 232, 25)];
    searchText.layer.cornerRadius = 12.5;
    searchText.layer.masksToBounds = YES;
    searchText.font = [UIFont systemFontOfSize:12];
    searchText.delegate = self;
    searchText.backgroundColor = [UIColor colorWithRed:236/255.0f green:236/255.0f blue:236/255.0f alpha:1.0];
    [searchText setTextColor:[UIColor whiteColor]];
    searchText.placeholder = @"搜索商品";// 再也不用在前面加上恶心的空格啦
    [backgroudLayer addSubview:searchText];
    
    
    UIImageView *searchIcon = [[UIImageView alloc] initWithFrame:CGRectMake(7, 2, 20, 20)];
    searchIcon.image = [UIImage imageNamed:@"search"];
    searchIcon.userInteractionEnabled = NO;
    
    // 就是这里了，将创建的icon直接赋给leftView就好了
    searchText.leftView = searchIcon;
    searchText.leftViewMode = UITextFieldViewModeAlways;
}

done。